Where shrimp come to die....

[Mustafa]

The cichlid substrate should be fine...just wash it first. Also...as the 90% water change solved your issues something clearly poisonous was in the water. Snails and shrimp react differently to environmental poisons so, yes, it's not unusual that one or the other species does fine while the other doesn't. As for the shrimp that still died after the water change...shrimp unfortunately don't recover very well after they have already been poisoned or otherwise damaged, so that explains it. Just don't change anything to that tank beyond this. It looks like you have fixed the problem...finally.

[TeriAnn]

Agreed, there will be no changes made in that tank for a while. I thought I had eliminated everything. I never suspected my RO water. From here on, nothing but distilled water will be used. Oddly enough, I was in my basement and it dawned on me, all my water pipes are copper. I have an API test for copper and no copper registered, maybe it was so minute the test did not catch it? In my area all homes have copper pipe. Are these shrimp sensitive to copper like freshwater shrimp?

[Mustafa]

Are these shrimp sensitive to copper like freshwater shrimp?

Yes, but copper is usually not a problem both for these shrimp and freshwater shrimp. Copper falls out of solution (combines with something else to become solid) at these high pH levels.